Jonathan D. Rockoff | Sun reporter

A growing number of health officials fear that investigators made a terrible mistake in blaming tomatoes for the sickening of more than 800 Americans, and they increasingly suspect jalapeno peppers, cilantro or some other food commonly found in Mexican restaurants, health officials involved in the investigation say.

The salmonella outbreak should be petering out if contaminated tomatoes were the cause, because tomatoes have a limited shelf life and many consumers have been avoiding them. Yet, the number of reported cases has continued to grow, and investigators have failed to identify the source.

Admission of a mistake, after consumers across the country shunned tomatoes and the food industry lost up to $250 million, could deepen criticism of a government food safety system that has been attacked for failing to prevent illnesses and deaths resulting from the contamination of a string of products, including peanut butter and bagged spinach, in recent years.

"It's bad, and I think everyone will be very apologetic" if it turns out tomatoes weren't the source, said Tim Jones, Tennessee's state epidemiologist, describing himself as "increasingly concerned" about whether tomatoes are to blame.

Failure to find the culprit, a month after authorities warned the nation, reflects the difficulty of tracing the source of microscopic bacteria in widely used food. It also underscores the weaknesses in a government safety net that critics say relies on short-staffed state health departments and turf-conscious federal authorities.

It could still turn out that tainted tomatoes caused the Salmonella saintpaul outbreak, believed to be the largest ever tracked in this country, with 810 people confirmed sick, including 25 in Maryland, as of last week.

On Friday, federal health officials said that investigators continued to find a strong association between tomatoes and the most recent confirmed illnesses. The officials said they were "keeping an open mind" about other possible sources, but other health officials said the hunt for alternate suspects is under way.

Investigators began retracing their steps last week, reinterviewing victims and revisiting restaurants, according to officials in five states. Investigators are broadening their questioning of those who became sick recently, because no one has yet found a tainted tomato.

"The current leading suspect - tomatoes - may not tell the full story," said Mike Landen, deputy state epidemiologist in New Mexico.

Other health officials said investigators could establish a different cause for the outbreak as early as this week.

If contaminated tomatoes are not the source, health officials worry about the possible recriminations for officials of the Food and Drug Administration, the Centers for Disease Control and Prevention, and state health departments. Consumers avoided tomatoes, restaurants emptied shelves and suppliers destroyed their stocks after the FDA issued a nationwide warning in early June.

The tomato industry probably will demand government reforms, said Jim Prevor, editor of Produce Business, a trade magazine that estimates that tomato farmers and distributors could lose $250 million in lost sales and destroyed supplies.

"The produce industry will insist on congressional hearings - that there will be a real investigation into how this was conducted," Prevor said. "This is a real disaster."

Even before its focus on tomatoes was questioned, the investigation was criticized by food specialists and industry observers because of delays and confusion in finding the source of the outbreak. Critics questioned investigators' methods and attacked a public health system that relies on state health departments of varying quality and federal health agencies unwilling to share information.

Health officials defended their investigation, saying that tainted tomatoes are especially difficult to trace because they do not carry bar codes and are often resold after being mixed with other produce.

"At this point, the investigation is moving toward critical answers. It wasn't doing that three weeks ago," said Michael Osterholm, an infectious diseases specialist at the University of Minnesota who advises federal and state health departments on food-borne outbreaks.

Investigators are looking at produce used frequently in salsa, guacamole and similar dishes because most of the roughly 20 clusters of those who became ill ate at Mexican restaurants, health officials said. Tomatoes are widely used in the dishes, which health officials say would explain their strong association with the outbreak and the early thinking that they were to blame.

Health officials fear that investigators from New Mexico and Texas, which led the early probe, might have made the basic mistake of failing to account for foods that are often eaten with tomatoes before identifying tomatoes as the likely salmonella source in late May.

Texas and New Mexico health officials say that all signs pointed to tomatoes and that they preferred to "err on the side of safety" to protect public health. Now, investigators in those states are looking at whether peppers, cilantro or other ingredients in salsa and guacamole might be responsible for the outbreak, though the federal government is still warning consumers to avoid certain tomatoes.

Mistakes in identifying the roots of food-borne illness are rare. In 1996, investigators initially identified California strawberries as the source of a Cyclospora outbreak that turned out to have been caused by Guatemalan raspberries. Last year, Taco Bell banned green onions during an E. coli outbreak that was later determined to have been the result of tainted lettuce.

"We're certainly still looking at the possibility that illnesses are associated with tomatoes, but we're also looking for other common foods and ingredients, including salsa, guacamole, other produce and other items," David Blythe, Maryland's state epidemiologist, said in a statement.